What they thought was a rusty box in their backyard was a safe with $52,000 worth of treasure

(CNN) For years Matthew and Maria Colonna-Emanuel thought a piece of rusty metal behind some trees in their backyard was just part of a cable or electrical box.

But it wasn't. It was a safe containing $52,000 in cash, gold and diamonds. And the story of how they discovered it -- and what the couple did next -- is remarkable.

The couple saw the metal box between some trees when they moved in to their Staten Island home in New York, but never paid much attention to it.

"I thought it was an electrical box," Matthew Colonna-Emanuel told CNN affiliate WCBS